極端降雨下堤防邊坡穩定可靠度探討-以荖濃溪沿岸堤防為例

游弘文(HUNG-WEN YU)

指導教授 ： 黃文昭

國立中央大學/工學院/土木工程學系/碩士(2015年)

摘要

本研究以水位高、淘刷深度、現地土壤摩擦角為變因，並排除如洪水溢頂、堤防內管湧等較不可能之破壞機制後，考慮堤防以邊坡滑動、擋土牆滑動與擋土牆傾倒三種可能發生的破壞機制，建立不同淘刷深度、堤內外水位高、現地摩擦角下之安全係數資料庫。利用這些資料，使用蒙地卡羅模擬(Monte Carlo simulation)隨機在設定的區間中生成各變因之數值，內插各組變因決定對應之安全係數，並對其結果進行統計分析。
對舊寮一號堤防而言，擋土牆滑動有最低的安全係數與最高破壞機率，然而邊坡滑動因為有較高的變異係數，故在可靠度分析中亦不可忽略其發生的可能性。相對而言，此一堤防不太可能發生擋土牆傾倒的破壞。對龜山堤防而言，其邊坡滑動反而有最高的可靠度指標而較不可能發生。另外兩種破壞模式中，因為擋土牆傾倒對水位差係數有較高的靈敏度，故在低水位差下，擋土牆較易發生滑動，反之則是傾倒較可能發生。

關鍵字

可靠度指標 ； 蒙地卡羅 ； 邊坡穩定 ； 極端降雨

並列摘要

Extreme weather has recently caused many disasters worldwide. In recent years, the condition about extreme rainfall by Typhoon has caused the loss of numerous human lives and properties in Taiwan. In fact, half of top ten record of rainfall has occurred in last ten years. In August 8, 2009, Taiwan suffered from serious floods during Typhoon Morakot. In this extreme rainfall event, Levees along the Laonong River basin between the confluences with Chokuo River and Ailiao River experienced catastrophic failure. Because the design of such levees does not consider the effects of extreme rainfall, failure had occurred with unexpected situations.
Our goal is to find the reliability index of the levee in this basin for assessing the stability of each levee. We considered the three possible major failure mechanisms (the slope sliding failure of the levee, and the sliding and overturning failures of the retaining wall) with the failure-triggering parameters (the water level, the scouring depth, and the in-situ angle of internal friction). After the database of the safety factor corresponding to each failure-triggering parameters has been generated, the safety factors can be obtained by Monte Carlo simulation under different situations. Finally, we can get the reliability index with mean value and variation by the results of MCS.
In Chiuliao 1st Levee, sliding failures of the retaining wall has largest probability, but we can’t ignore the probability of slope sliding failure due to its high variability. In Gueishan Levee, slope sliding failure has highest reliability index. In low water level difference, sliding failures of the retaining wall has lowest reliability index. In high water level difference, overturning has lower reliability index than sliding failures of the retaining wall.

參考文獻

11. 謝正倫、林家興、曾志民、李心平、邱禎龍，「莫拉克颱風河道破堤特性分析」，中華防災學刊，第2期，第73-81頁(2010)

7. 褚炳麟、潘進明、張國雄，「台灣西部卵礫石層現地之大地工程性質」，地工技術，第55期，第47-58頁 (1996)。

8. 劉建邦、蔡文豪、謝國正、林家輝、張東宸，「南部地區八八水災水利設施勘災及改善對策」，地工技術，第122期，第95-104頁 (2009)。

12. Bishop, A. W., "The Use of Slip Circle in the Stability Analysis of Slopes," Geotechnique, Vol.5, No.1, pp.7-17 (1955).

15. Schmocker, L., Hager, W.H., "Modelling dike breaching due to overtopping," Journal of Hydraulic Research, T.47, No.5, pp.585-597 (2009).